This invention relates generally to machine-human interfaces and in particular to an electrical circuit which is capable of readily altering the function of a switch. In certain machines it is desirable to have switch convey a selectable output to associated electronics. It is also desirable to create some sort of markings or indicia on the switch which will convey to the user what the presently selected output of the switch is.
By way of example, a beverage dispenser of the type commonly found in fast food establishments may have a plurality of spigots for dispensing different flavors of soft drinks. A switch is provided to actuate the appropriate valves to start and stop flow of flavored syrup and carbonated water to a selected spigot. Some label or indicia is placed on or near the switch to tell the user what flavor will be supplied if that particular switch is activated. There may be situations where the proprietor of the dispenser may wish to change the flavor supplied upon activation of a switch. For example, the supply of one flavored syrup may be exhausted. Rather than taking that switch and its spigot out of service or having customers suffer the frustration of futile attempts to obtain the exhausted flavor, the proprietor may prefer to change the switch and spigot to another flavor. To do this the signal obtained from the switch must control a different set of valves. Obviously this could be done by rewiring the switch to the new set of valves but the time, training and tools required to do so make this approach impractical. A simpler alternative would be to alter the character of the output from the switch and allowing external electronics to sense the altered signal and select the appropriate set of valves. At the same time, users have to be alerted to what the new flavor is, i.e, new indicia on or near the switch must be provided. The present invention provides a switch that accomplishes the foregoing.
This invention provides an electric circuit whose output can be readily altered. The circuit has a substrate that includes a magnet layer and an insulative switch layer laminated together. The exposed surface of the switch layer has a set of conductors disposed on it. The conductors define a plurality of switch leads which terminate at switch contacts. The switch leads extend onto a tail portion of the switch layer for connection to external electronics. An overlay is removably mounted on the substrate. The overlay comprises a decal, retainer plate and insulative shorting layer laminated together. The retainer plate is made of magnetic material. When the overlay is placed on the substrate the magnetic attraction between the magnet layer and the retainer plate will hold the overlay on the substrate. The exposed surface of the shorting layer has a set of conductors on it defining a shorting strap. The shorting strap may include one or more shorting pads which align with the switch contacts when the overlay is installed on the substrate. The shorting strap is arranged to engage at least two of the switch leads to electrically connect the two switch leads. Multiple overlays having different shorting strap configurations are provided to connect different pairs of the switch leads. The decal of the overlay may be suitable indicia on it to advise what output will result from the shorting strap arrangement on that overlay.